The purpose of this assessment probe is to elicit students’ ideas about the surface of Earth. It is designed to find out if students recognize that most of Earth’s surface is covered by water and helps students learn about the ratio of water to land on Earth. After learning this, students can discuss whether our planet should be called Planet Earth or Planet Ocean. They can support their opinions with evidence. The probe is best used with grades 3-8. A materials list, teacher background information, references, assessment, and outcomes are provided. This book selection includes the Table of Contents, Foreword, Preface, Acknowledgments, About the Authors, Introduction, and Index.